Ignition cable

ABSTRACT

An ignition cable for use with vehicle engines having spark ignition having the improved construction comprising a flexible resistive conductor means and a special flexible conductive coating means thereover which is capable of providing the ignition cable means with sustained resistance to temperatures of about 500*F and higher as encountered, for example in under-thehood automotive engine applications.

United States Patent 1 1 Wiley et a1.

[ Mar. 11, 1975 41 IGNITION CABLE [75] Inventors: Robert Emerson Wiley; James John Coniglio, both of Port Huron, Mich.

[731 Assignee: Acheson Industries, Inc., Port Huron, Mich.

[22] Filed: May 29, 1973 [21] Appl. No.: 364,751

[52] US. Cl...... 338/214, 174/102 SC, 174/120 SC, 252/511, 338/60, 117/232 [51] Int. Cl HOlg 3/00 [58] Field of Search 338/214, 66; 174/120 SC, 174/102 SC; 252/511, 514; 117/232 [56] References Cited UNITED STATES PATENTS 2,377,153 5/1945 Hunter 174/120 SC 2,744,988 5/1956 Tiermann 174/102 SC 2,983,624 5/1961 Thompson 117/68 3,284,751 11/1966 Barvier 338/66 3,573,230 3/1971 Van Voorhees 252/514 FOREIGN PATENTS OR APPLICATIONS 127,197 11/1944 Australia 252/511 OTHER PUBLICATIONS Rose, The Condensed Chemical Dictionary," Sixth Edition, 1963 Reinhold, N.Y..p. 1218+v.

Viton Fluoroelastomer DuPont Brochure, A4271], 6-65, pgs. 1-22.

Bowman, Solution Coatings of Viton, DuPont Brochure of Viton, No. 16, 3/66, pgs. l-12.

Primary ExaminerE. A. Goldberg Attorney, Agent, or Firm-Harness, Dickey & Pierce [57] ABSTRACT An ignition cable for use with vehicle engines having spark ignition having the improved construction comprising a flexible resistive conductor means and a special flexible conductive coating means thereover which is capable of providing the ignition cable means with sustained resistance to temperatures of about 500F and higher as encountered, for example in under-the-hood automotive engine applications.

20 Claims, 1 Drawing Figure NON-VULCANIZED SEMI-CONDUCTIVE FLU OROE LA STOMER PATENTED MRI 1 I975 NON -VULCANIZED SEMI-CONDUCTWE FLUOROELASTOMER 1 IGNITION CABLE BACKGROUND OF THE INVENTION actuated devices, capacitor constructions, and the like wherein the coating disclosed herein may be highly useful.

The state of the art is indicated by the following references: US. Pat. Nos. 3,284,751; 3,573,230; 2,983,624; 3,025,185; 2,968,649; 3,132,124; 3,051,677; DuPont Viton Bulletin No. 116 identified as A 47946/3-66, entitled Solution Coatings of Viton" by J. M. Bowman; and, DuPonts technical bulletin identified as A427l1/6-65, entitled The Engineering Properties of Viton Fluoroelastomer.

Accordingly, it is a primary object of this invention to provide a new improved ignition cable construction which includes a special thermally stable covering material as a part of the ignition cable construction.

Another object of the present invention is to provide a new covering or coating composition for use with ignition cable constructions or for other uses.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 illustrates in perspective using cut-away portions, an ignition cable construction in accordance with the invention.

SUMMARY OF THE INVENTION Briefly stated, the present invention concerns an ignition cable means having an improved construction comprising a flexible resistive conductor means for conducting electrical current to provide ignition, a flexible conductive coating means generally surrounding the resistive conductor means, said coating being made from a composition comprised of about 50 percent to about 90 percent by weight of fluoroelastomer means for providing the coating with sustained thermal stability for continuous exposure to temperatures of about 500F., and for shorter term exposure to temperatures of 600650F., about percent to about 50 percent by weight of conductive pigment means for providing conductivity to the coating, and zero to about percent by weight of flow control agent means for facilitating application usage of the coating, and said coating including about l percent to about 50 percent by weight total solids of the above in a solvent carrier. The invention also concerns a novel coating composition or covering material wherein through the unique combination of a fluoroelastomer material capable of resisting high temperatures and a special pigmentation means such as a conductive pigment or a fluorocarbon pigment, a highly useful product is obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, FIG. .1 illustrates an ignition cable construction designated 10 which is comprised of graphite impregnated fiberglass conductors 12, a braid material 14 of rayon, cotton or the like woven around the elements 12 to hold same together. and a special covering material or coating composition 16 surrounding the core of the ignition cable formed by the conductors l2 and braid 14. The covering material or sheath 16 is a high temperature resistant special electrically conductive layer and will be described in more detail below.

Overlying the covering or coating layer 16 is a strip coating 18 formed for example of a material which includes graphite. The strip coating 18 is optional. It may be used for the function of allowing a conventional overlying insulating material 20, further braid material 22 and insulating jacket 24 to be readily stripped or removed from the nonmetallic conductor means so that electrical connections with a terminal can be made as desired. It is to be understood that the strip coating, insulating layer and/or the insulatingjacket, as well as the braiding layers can be made from any number of different materials so long as they are suitably resistant to high temperature and so long as they do not detrimentally effect the necessary electrical properties of the ignition cable construction.

The crux of the ignition cable construction in accordance with this invention lies in the enveloping of the flexible conductors 12 within the special covering or coating sheath 16. The braid material 14 may be applied prior to or subsequent to the application of the covering sheath 16, however, preferably the braid material 14 is applied to the flexible conductors 12 before the covering 16 is applied.

The covering or coating 16 is applied to envelop the flexible conductors 12 using a suitable applicator which coats the covering 16 onto the ignition cable from a solvent solution with the solvent later being driven off or evaporated from the coating or layer 16. For example, the coating or layer 16 is applied to the cable by dipcoating the cable in a solution of the coating which is maintained within the borad range of approximately about ZOO-5,000 centipoise and preferably within the range of about 5002,000 centipoise.

The coating composition for forming the layer 16 contains total solids within the broad range of about 96 percent to about percent by weight of the total weight of the coating composition and preferably the percent solids is maintained within the range of about /2 percent to about 20 percent by weight.

The fluoroelastomer material means used in the coating should be present within the broad range of about 8 percent to about 95 percent by weight of the coating solids and preferably from about 50 percent to about percent by weight, with best results being obtained in the range of 60-80 percent. This fluoroelastomer material provides the special function of endowing the coating with high temperature resistance or great thermal stability, that is, resistance to temperatures in excess of 400F. and, particularly this temperature resistance has been found to be effective and operative within the range of about 400F. up to about 600F. and higher. The fluoroelastomer material used in the invention should be one which provides this high temperature resistance and which is also sufficiently flexible for use in ignition cable constructions while at the same time possessing the property of being able to operate as an effective binder material for the applied coating. Particularly suitable material for use as the fluoroelastomer herein may be described as vinyl/olefinic fluoroelastomeric polymers, vinyl-fluorocarbon elastomeric copolymers, vinylidene/fluoro-olefinic elastomeric polymers, and C -C olefinic/fluorocarbon elastomeric copolymers. A preferred material is the vinylidene fluoride/hexafluoropropene copolymer fiuoroelastomer. Commercially available fiuoroelastomers which may be used are Viton (DuPont trademark) and Fluorel (3M Company trademark). Still further fluoroelastomers which may be used herein are described in U.S. Pat. Nos. 2,968,649, 3,051,677, and 3,172,124, the disclosures of which are incorporated herein by refcrcncc.

The pigment means or particles for use in the coating 1 16 should be present within the broad range of about 5 percent to about 92 percent by weight of the total solids of the coating and preferably this range should be from about percent to about 50 percent by weight, with best results being obtained in the range of 20-40 percent. Particularly suitable pigments for use in the coating are various finely particulated pigments such as graphite, conductive carbon black, silver particles, copper particles, noble metal particles, tin oxide, and fluorocarbon polymer particle pigments. Particularly suitable conductive pigments are finely divided graphite, silver and, copper particles. The fluorocarbon pigment particles add lubricity to the finished coating.

The flow control agent used in the coating may be present broadly within the range of zero up to about percent by weight of the coating solids and preferably the flow control agent is present in the range of about 0.05 percent up to about 10 percent by weight of the coating solids. Particularly suitable materials for use as the flow control agent are finely divided materials selected from the group consisting of silicas, finely di-' vided clays, and silicates. Specific materials for this case are Cab-o-sil and Bentone.

The solvent or carrier material used for forming a fluid dispersion of the coating solids may satisfactorily be selected from any number of different solvents such as methyl-ethyl ketone, acetone, various other ketone type solvents, dimethylformamide, and numerous other organic solvent materials. The solvent forms the balance of the coating composition when the coating is formulated in a solution having a total solids content between about k percent and 50 percent by weight solids as referred to above. During and/or after application of the coating, the solvent is essentially driven off or evaporated leaving the applied coating.

A curing agent may also optionally be used in the coating although it is not preferred. For this purpose various amino type curing agents and the like may be used.

The continuous operating temperature for coatings formed in accordance with the above is about 500F. For short term exposure coatings withstand temperatures as high as about 600650F and higher. Thus coatings so formed are highly useful in under-the-hood applications for the newly specified automotive engine requirements, where under-the-hood temperature specifications for automotive usage are in excess of 400F. At the least, specifications for such under-thehood applications require that ignition cable constructions be operative at temperatures in excess of 400F. for sustained periods of time.

Coating compositions suitable for use in manufacture of thermally stable ignition cables are prepared by dispersing the graphite or conductive carbon particles in solutions of the selected fluoroelastomer. The amount of solvent used should be suflicient to provide a suitable dispersing medium for the solid particles. The particlesv may be dispersed in all or part of the elastomer solution, for example by means such as use of ball or pebble mills, double blade mixers, or impeller mixers. Adjustment of the consistency of the composition to that suitable for application to the cable may be effected by such means as adjusting the proportion of solvent, adjusting the temperature, or incorporating a bodying agent or flow control ingredient in suitable amount.

The electrical resistance of the coating formed in the ignition cable structure is determined by the coating thickness, by the particular conductive particles used, and the ratio of conductive particles to elastomer, i.e., the pigment: binder ratio. The exact level selected will be dependent on the core resistance as well as on other characteristics of the cable, such as the elastomer covering, the dimensions, etc. Generally, coatings in the resistance range between 500 ohms and 30,000 ohms per square, as evaluated by the technique herein described, can be adapted to produce ignition cables having desirable electrical characteristics.

Resistance character of coating compositions can be evaluated by forming dried or cured coatings under uniform conditions, upon which the electrical resistance measurements can be made. It is convenient to deposit the coatings from compositions containing about 13.5 percent total solids by use ofa blade coating device which will form on a glass plate layers of predetermined thickness. Measurements herein have been made at a dry coating thickness of 0.0005 inch, after curing for 10 minutes at 300F.

The electrical resistance was measured using a special fixture which gave data in ohms per square. The resistance measurement was made with a suitable precision ohmmeter.

Examples illustrating the invention are formulated as designated in Table I. For comparative purposes dispersions were prepared as described, and electrical resistance measured on films 0.0005 inch thick after cure at 300F. for 10 minutes. The resistance per square is indicated as well as totalsolids content, and the percentage of conductive pigment in the dry film.

The conductive carbon black was proprietary conductive furnace black.

TABLE I EXAMPLES 1-6 (Parts by Weight) Ingredient l 2 3 4 5 6 Graphite 200 mesh 36.8 ll.l 6.4 4.5 18 5 9.4 Conductive Black [4.8 8.5 6.0 7 4 12.5 Fumed Silica 6.2

TABLE l- Continued EXAMPLES 1-6 (Parts by Weight) Ingredient g l 2 3 4 5 6 Fluoroelastomer A v 74.1

Fluoroelastomer B 63.2 85.1 71.9 Fluoroelastomer C 74.1

Fluoroelastomer D 89.5

Methyl Ethyl Ketone 533 641 641 641 533 576 Total Solids 7: 15.8 13.5 13.5 13.5 15.8 14.8 Proportion of con- 36.8 25.9 14.9 10.5 25.9 21.9

ductive particles in dry film 1 Resistance ohms 1,000 790 5,400 23,000 1,200 1,450

EXAMPLE 7 5. The invention of claim 1 wherein,

An ignition cable was fabricated using a composition in accordance with the invention. A conventional graphite-impregnated fiberglass conductor, encased with a braided sheath of glass fibers, was coated with the composition of Example 6 by dipping and passing through a wiping device which removed excess material. The coated strand was oven dried and again passed through the coating bath, the wiping device, and the drying oven, to leave over the conductor a layer of conductive elastomeric coating. The electrical resistance of the coated strand was 5,000 ohms per foot. Fabrication of the ignition cable was completed by applying a lubricating strip coating and then extruding a silicone elastomer to form an insulating and protective outer layer.

While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. In an ignition cable for use with vehicle engines having spark ignition, the improved construction comprising:

a flexible resistive conductor means for conducting electrical current to provide ignition, a flexible coating layer having controlled electrical resistance generally surrounding the resistive conductor means, said layer being comprised of, about 50 percent to about 90 percent by weight of fluoroelastomer providing the coating with sustained thermal resistance on exposure to temperatures of about 500 F or higher,

about 10 percent to about 50 percent by weight of conductive pigment for providing conductivity to the coating, and

about 0.05 percent to about percent by weight of flow control agent for facilitating application usage of the coating.

2. The invention of claim 1 wherein,

said fluoroelastomer is an elastomeric material selected from at least one of the group consisting of fluorinated and fluorochlorinated polymers.

3. The invention of claim 1 wherein,

said conductive pigment means is a finely particu-' 65 lated material selected from at least one of the group consisting of graphites and carbons. 4. The invention of claim 1 wherein,

said flow control agent means is a finely divided material selected from at least one of the group consisting of the silicas and silicates.

said flow control agent means is present from about 0.05 percent to about 10 percent by weight of total solids.

6. In an electrically conductive device, the improved construction comprising:

a flexible resistive conductor means for conducting electrical current,

a flexible conductive coating means generally overlaying the resistive conductor means, said coating being made from a composition essentially consisting of, about 50 percent to about 90 percent by weight of non vulcanized fluoroelastomer means for providing the coating with sustained resistance to high temperatures in the range of about 500 F, about 10 percent to about 50 percent by weight of conductive pigment means for providing conductivity to the coating, and said coating composition including about /2 percent to about 50 percent by weight total solids of the above in a solvent carrier.

7. The invention of claim 6 wherein,

said fluoroelastomer means is an elastomeric material selected from at least one of the group consisting of fluorinated and fluorochlorinated olefin polymers.

8. The invention of claim 6 wherein, said flow control agent means is a finely divided material selected from at least one of the group consisting of the silicas and silicates.

9. In an electrically conductive device, the improved construction comprising:

a flexible resistive conductor means for conducting electrical current,

a flexible conductive coating means generally overlaying the resistive conductor means, said coating being made from a composition comprised of, about 60 percent to about percent by weight of fluoroelastomer means for providing the coating with sustained resistance to high temperatures in the range of about 500 F, about 40 percent to about 20 percent by weight of conductive pigment means for providing conductivity to the coating, and 0.05 percent to about 10 percent by weight of flow control agent means for facilitation application usage of the coating, and said coating composition including about V2 percent to about 50 percent by weight total solids of the above in a solvent carrier.

10. The invention of claim 9 wherein,

said total solids content is from about 5 percent to about 25 percent.

11. man ignition cable'for use with vehicle engines having spark ignition, the improved construction comprising:

a flexible resistive conductor means for conducting electrical current to provide ignition, a flexible coating layer having controlled electrical resistance generally surrounding the resistive conductor means,

said layer being comprised of, about 50 percent to about 90 percent by weight of fluoroelastomer providing the coating with sustained thermal resistance on exposure to temperatures of about 500 F or higher, about 10 percent to about 50 percent by weight of conductive pigment for providing conductivity to the coating, and a small amount greater than zero to about l percent by weight of flow control agent for facilitating application usage of the coating. 12. In an electrically conductive device, the improved construction comprising:

a flexible resistive conductor means for conducting electrical current, a flexible conductive coating means generally overlaying the resistive conductor means, said coating being made from a composition comprised of, about 50 percent to about 90 percent by weight of fluoroelastomer means for providing the coating was sustained resistance to high temperatures in the range of about 500 F,

about percent to about 50 percent by weight of conductive pigment means for providing conductivity to the coating, and

a small amount greater than zero up to about percent by weight of flow control agent means for facilitating application usage of the coating, and

8 said coating composition including about /2 percent to about 50 percent by weight total solids of the above in a solvent carrier. 13. The invention of claim 12 wherein, said conductive pigment means is a finely particulated material selected from at least one of the group consisting of graphite and conductive carbon. 14. The invention of claim 12, wherein, said conductive pigment means is a finely particulated material selected from at least one of the group consisting of graphite, silver, copper, and

noble metals.

15. The invention of claim I wherein,

said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.

16. The invention of claim 6 wherein,

said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.

17. The invention of claim 12 wherein,

said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.

18. The invention of claim 14 wherein,

said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.

19. The invention of claim 6 wherein,

said fluoroelastomer is an elastomeric material selected from at least one of the group consisting of a fluorinated polymer and a fluoro-chlorinated polymer.

20. The invention of claim 12 wherein,

said fluoroelastomer is an elastomeric material selected from at least one of the group consisting of a fluorinated polymer and a fluoro-chlorinated polymer. 

1. In an ignition cable for use with vehicle engines having spark ignition, the improved construction comprising: a flexible resistive conductor means for conducting electrical current to provide ignition, a flexible coating layer having controlled electrical resistance generally surrounding the resistive conductor means, said layer being comprised of, about 50 percent to about 90 percent by weight of fluoroelastomer providing the coating with sustained thermal resistance on exposure to temperatures of about 500* F or higher, about 10 percent to about 50 percent by weight of conductive pigment for providing conductivity to the coating, and about 0.05 percent to about 15 percent by weight of flow control agent for facilitating application usage of the coating.
 1. IN AN IGNITION CABLE FOR USE WITH VEHICLE ENGINES HAVING SPARK IGNITION, THE IMPROVED CONSTRUCTION COMPRISING: A FLEXIBLE RESISTIVE CONDUCTOR MEANS FOR CONDUCTING ELECTRICAL CURRENT TO PROVIDE IGNITION, A FLEXIBLE COATING LAYER HAVING CONTROLLED ELECTRICAL RESISTANCE GENERALLY SURROUNDING THE RESISTIVE CONDUCTOR MEANS, SAID LAYER BEING COMPRISED OF, ABOUT 50 PERCENT TO ABOUT 90 PERCENT BY WEIGHT OF FLUOROELASTOMER PROVIDING THE COATING WITH SUSTAINED THERMAL RESISTANCE ON EXPOSURE TO TEMPERATURES OF ABOUT 500* F OR HIGHER, ABOUT 19 PERCENT TO ABOUT 50 PERCENT BY WEIGHT OF CONDUCTIVE PIGMENT FOR PROVIDING CONDUCTIVITY TO THE COATING, AND ABOUT 0.05 PERCENT TO ABOUT 15 PERCENT BY WEIGHT OF FLOW
 2. The invention of claim 1 wherein, said fluoroelastomer is an elastomeric material selected from at least one of the group consisting of fluorinated and fluorochlorinated polymers.
 3. The invention of claim 1 wherein, said conductive pigment means is a finely particulated material selected from at least one of the group consisting of graphites and carbons.
 4. The invention of claim 1 wherein, said flow control agent means is a finely divided material selected from at least one of the group consisting of the silicas and silicates.
 5. The invention of claim 1 wherein, said flow control agent means is present from about 0.05 percent to about 10 percent by weight of total solids.
 6. In an electrically conductive device, the improved construction comprising: a flexible resistive conductor means for conducting electrical current, a flexible conductive coating means generally overlaying the resistive conductor means, said coating being made from a composition essentially consisting of, about 50 percent to about 90 percent by weight of non vulcanized fluoroelastomer means for providing the coating with sustained resistance to high temperatures in the range of about 500* F, about 10 percent to about 50 percent by weight of conductive pigment means for providing conductivity to the coating, and said coating composition including about 1/2 percent to about 50 percent by weight total solids of the above in a solvent carrier.
 7. The invention of claim 6 wherein, said fluoroelastomer means is an elastomeric material selected from at least one of the group consisting of fluorinated and fluorochlorinated olefin polymers.
 8. The invention of claim 6 wherein, said flow control agent means is a finely divided material selected from at least one of the group consisting of the silicas and silicates.
 9. In an electrically conductive device, the improved construction comprising: a flexible resistive conductor means for conducting electrical current, a flexible conductive coating means generally overlaying the resistive conductor means, said coating being made from a composition comprised of, about 60 percent to about 80 percent by weight of fluoroelastomer means for providing the coating with sustaIned resistance to high temperatures in the range of about 500* F, about 40 percent to about 20 percent by weight of conductive pigment means for providing conductivity to the coating, and 0.05 percent to about 10 percent by weight of flow control agent means for facilitation application usage of the coating, and said coating composition including about 1/2 percent to about 50 percent by weight total solids of the above in a solvent carrier.
 10. The invention of claim 9 wherein, said total solids content is from about 5 percent to about 25 percent.
 11. In an ignition cable for use with vehicle engines having spark ignition, the improved construction comprising: a flexible resistive conductor means for conducting electrical current to provide ignition, a flexible coating layer having controlled electrical resistance generally surrounding the resistive conductor means, said layer being comprised of, about 50 percent to about 90 percent by weight of fluoroelastomer providing the coating with sustained thermal resistance on exposure to temperatures of about 500* F or higher, about 10 percent to about 50 percent by weight of conductive pigment for providing conductivity to the coating, and a small amount greater than zero to about 15 percent by weight of flow control agent for facilitating application usage of the coating.
 12. In an electrically conductive device, the improved construction comprising: a flexible resistive conductor means for conducting electrical current, a flexible conductive coating means generally overlaying the resistive conductor means, said coating being made from a composition comprised of, about 50 percent to about 90 percent by weight of fluoroelastomer means for providing the coating was sustained resistance to high temperatures in the range of about 500* F, about 10 percent to about 50 percent by weight of conductive pigment means for providing conductivity to the coating, and a small amount greater than zero up to about 15 percent by weight of flow control agent means for facilitating application usage of the coating, and said coating composition including about 1/2 percent to about 50 percent by weight total solids of the above in a solvent carrier.
 13. The invention of claim 12 wherein, said conductive pigment means is a finely particulated material selected from at least one of the group consisting of graphite and conductive carbon.
 14. The invention of claim 12, wherein, said conductive pigment means is a finely particulated material selected from at least one of the group consisting of graphite, silver, copper, and noble metals.
 15. The invention of claim 1 wherein, said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.
 16. The invention of claim 6 wherein, said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.
 17. The invention of claim 12 wherein, said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.
 18. The invention of claim 14 wherein, said fluoroelastomer is a vinylidene fluoride-hexafluoropropene copolymer type material.
 19. The invention of claim 6 wherein, said fluoroelastomer is an elastomeric material selected from at least one of the group consisting of a fluorinated polymer and a fluoro-chlorinated polymer. 